Proteins and Amino Acids Practice Problems

Write the appropriate structure of a DNA segment that contains 4 nucleotides with the sequence shown below.

(3' end) T-A-C-G (5' end)

Provide the major product of the reaction given below.

True or False. The bonds between the carbonyl carbon and nitrogen in the backbone of a peptide can freely rotate.

When a decapeptide is partially hydrolyzed, the following peptides are produced:

(i) Ser, Trp            (ii) His, Val, Gln        (iii) Ile, Tyr          (iv) Glu, Asn, Pro

(v) Val, Ile, His     (vi) Trp, Glu, Ser      (vii) Pro, Gln

What is the sequence of the decapeptide if it reacts with Edman's reagent to produce PTH-Ser?

Specify the peptides generated by the cleavage of Ser-Gln-Arg-Val-Ile-Trp-Phe-Lys-Pro-Cys-Lys-Tyr-Met-Glu with trypsin.

How would a protein found in the nonpolar interior of a membrane fold?

After being treated with maleic anhydride, trypsin only cleaved the given polypeptide on the C-side of arginine and not on the C-side of lysine. Why? 

A polypeptide composed of 13 unique amino acids undergoes partial hydrolysis to yield the following peptides:

(i) Arg, Gln, Thr   (ii) Leu, Arg            (iii) Phe, Cys, Gln       (iv) Thr, Arg

(v) Glu, Lys, Pro  (vi) Met, Ala, Pro     (vii) Leu, Tyr, Arg        (viii) Gln, Lys, Cys

(ix) Pro, Met        (x) Lys, Glu, Gln       (xi) Gln, Phe                (xii) Val, Ala

If the reaction of the intact polypeptide with carboxypeptidase A releases Leu, what is the sequence of the polypeptide? 

Which tripeptide has a more readily cleaved C-terminal peptide bond by Carboxypeptidase A and why? Gly-Val-Glu or Gly-Val-Leu

Determine the alkyl halide needed to prepare isoleucine via acetamidomalonic ester synthesis.

Which of the following alkyl halides can be used to produce tyrosine via acetamidomalonic ester synthesis? 

The herbicide shown below is an ester derivative of glyphosate. Although only a small amount of the herbicide is required to kill a plant, it shows little toxicity against humans. Assuming that it kills plants by inhibiting an enzyme needed for the synthesis of phenylalanine, suggest why this powerful herbicide has little effect on humans.

Show how you would prepare alanine via bromination followed by amination.

Show how to prepare any of the standard amino acids from the compound shown below. You can use any reagents you need to accomplish the synthesis.

Show how you would utilize reductive amination to form valine from an appropriate α-ketoacid.

Show how to prepare any of the standard amino acids from the compound shown below. You can use any reagents you need to accomplish the synthesis.